Conventional small motorized positive-displacement diaphragm pumps use a mechanically-actuated electrical switch to control pump operation based on system pressure. Such a mechanical switch disadvantageously applies either full power or no power to a pump motor, causing the system pressure to pulse.
Improved systems utilize solid-state PWM (pulse width modulation) type power control, implemented with proportional pressure sensing for closed-loop operation, to vary the motor speed in proportion to the system demand for flow. This approach stabilizes system pressure in spite of changes in flow demand, reducing or eliminating system pressure pulsing. Existing designs for such pressure control provide the corresponding control circuitry integral with the pump being controlled.
Such an integral scheme requires a user to purchase the pump and controller both, to obtain the benefits of the controller. In other words, a user cannot use a pump of the user's own choosing and mate it with the closed-loop pressure controller because the controller is integral with or permanently attached to another pump, as manufactured.